JPH0616850A - Biaxially oriented laminated film - Google Patents

Abstract

PURPOSE:To provide a biaxially oriented laminated film on the surface of which desired chipping-resistant protrusions are formed at good efficiency to impart thereto a desired surface profile and which can exhibit excellent windability, is excellent in dropout resistance as a magnetic medium, and has excellent adhesion to magnetic layer. CONSTITUTION:The film has an at least three-layer laminated structure prepared by coextrusion, contains particles in at least one of the outermost layers, satisfies the relationship: 0.2d<=t<=10d (wherein d is the mean particle diameter of the particles, and t is the thickness of an outermost layer), has 3X10<3>-2X10<5>/mm<2> protrusions on the surface or contains 3X10<3>-1.5X10<5>/mm<2> particles having diameters satisfying the above relationship and having a coating layer based on a water-soluble or water-dispersible resin on at least either surface.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a biaxially oriented laminated film.

[0002]

2. Description of the Related Art As a biaxially oriented laminated film, for example, a biaxially oriented polyester film, a film in which polyester contains substantially spherical silica particles derived from colloidal silica is known (for example, Japanese Unexamined Patent Publication (Kokai)). 59
No. 171623).

However, with the increase in the process speed of the film processing process, particularly the magnetic layer coating / calendering / winding process for magnetic media applications, the cassette assembling process, etc., the film surface, especially minute irregularities, is formed on the film by the contacting rolls or guides. There was a drawback that the film surface was easily scraped off. Further, the conventional one has a drawback that the image quality, that is, the S / N (signal / noise ratio) is insufficient because the image quality is deteriorated during dubbing as the dubbing speed is increased by high-speed magnetic field transfer.

In order to solve such a drawback, the outermost layer of the laminated film is made thin, and particles having a relatively large particle diameter relative to the layer thickness are contained, and the layer thickness and the particle diameter of the particles are specified. A biaxially oriented laminated film has been proposed in which minute protrusions that are difficult to be scraped off are formed on the surface of the film according to the above relationship (JP-A-2-77431).

[0005]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems in the prior art and, at the same time, discloses in Japanese Patent Laid-Open No. 2-7.
It is a further improvement of the technology proposed in Japanese Patent No. 7431, further improving the micro-protrusions on the surface of the film to further improve the winding characteristics particularly when processed for magnetic media applications and the dropout characteristics when used for magnetic media applications. It is also an object of the present invention to provide a biaxially oriented laminated film having improved adhesion to the magnetic layer.

[0006]

A biaxially oriented laminated film of the present invention for this purpose is a biaxially oriented laminated film having a laminated structure of at least three or more layers by coextrusion, and at least one outermost layer of the biaxially oriented laminated film. Containing particles, the average particle diameter d (nm) of the particles and the layer thickness t (n
m) is 0.2d ≦ t ≦ 10d, and the number of protrusions on the film surface on the outermost layer side is 3 × 1.
It is 0 ^{3 to} 2 × 10 ⁵ pieces / mm ² , and a coating layer having a water-soluble or water-dispersible resin as a main component is further provided on at least one side thereof.

Another biaxially oriented laminated film of the present invention is a biaxially oriented laminated film having a laminated structure of at least three layers by coextrusion, and contains particles in at least one outermost layer, Average particle size d of the particles
(Nm) and the layer thickness t (nm) of the outermost layer are 0.2d ≦ t ≦ 10d, and the number of particles having a particle size satisfying the relationship is 3 × 10 ^3.
A to 1.5 × 10 ⁵ cells / mm ^2, further to at least one side, it consists of those in which a coating layer mainly composed of water-soluble or water-dispersible resin.

First, the film of the present invention must have a laminated structure of at least three layers. If there are 3 or more layers,
Four or five layers may be used, but a three-layer structure is preferable because the effect of the present invention is further improved. However, a single-layer or double-layer film cannot obtain good winding characteristics and good dropout characteristics when used as a magnetic medium.

Next, in the film of the present invention, the above-mentioned layers constituting the film are laminated by coextrusion, and the laminated film is biaxially oriented. As a constitution of the laminated film, at least one layer may be biaxially oriented. However, in the film of the present invention, since all layers are oriented biaxially, in addition to the strength property, the winding property and the drop property are Particularly preferable characteristics are obtained for the out characteristics.

The polymer constituting the biaxially oriented laminated film of the present invention is not particularly limited, but polyester is preferable for magnetic media applications. The polyester is not particularly limited, but ethylene terephthalate, ethylene α,
β-bis (2-chlorophenoxy) ethane-4,4′-
It is particularly preferable when at least one structural unit selected from dicarboxylate and ethylene 2,6-naphthalate units is the main constituent. Of these, polyesters containing ethylene terephthalate as a main constituent are particularly preferable. Two or more kinds of polyesters may be mixed, or a copolymerized polymer may be used, as long as the present invention is not impaired.

In the outermost layer on at least one side of the biaxially oriented laminated film of the present invention, firstly, particles have a relationship between the average particle diameter d (nm) of the particles and the layer thickness t (nm) of the outermost layer. Is contained so that 0.2d ≦ t ≦ 10d. If t is smaller than 0.2d, dropout increases, and if t is larger than 10d,
Winding characteristics are deteriorated due to vertical wrinkles.

Due to the inclusion of the above-mentioned particles, in the biaxially oriented laminated film of the present invention, the number of protrusions on the film surface on the outermost layer side is 3 × 10 ³ to 2 × 10 ⁵ pieces / mm ² . In this way, by setting a specific number of film surface protrusions, it is possible to obtain both good winding characteristics and dropout characteristics. The number of protrusions is 3 × 10 ³ / mm ²
When it is less than 2, dropout increases, and when it exceeds 2 × 10 ⁵ pieces / mm ² , winding deviation occurs and winding characteristics deteriorate.

Further, in the biaxially oriented laminated film of the present invention, the number of particles having a particle size satisfying the above relation is 3 × 10.
It is contained so as to be ^{3 to} 1.5 × 10 ⁵ pieces / mm ² . In this way, by setting the number of particles having a particle diameter satisfying a specific relationship between the particle diameter of the particles and the layer thickness of the outermost layer within a specific range, first, the desired minute projections on the film surface are formed by the contained particles themselves. Are efficiently formed.

In the biaxially oriented laminated film of the present invention, since the outermost layer containing particles is formed into a thin layer,
The protrusion forming action also appears from the intermediate layer to the outermost thin layer.
Therefore, the number of particles having a particle size satisfying the relation of the above formula is 3 ×
By containing it so as to be 10 ^{3 to} 1.5 × 10 ⁵ pieces / mm ² , the number of protrusions on the film surface should be set within the range of approximately 3 × 10 ³ to 2 × 10 ⁵ pieces / mm ² described above. Is possible.

Further, in the biaxially oriented laminated film of the present invention, a coating layer containing a water-soluble or water-dispersible resin as a main component is provided on at least one side. By providing this coating layer, the adhesiveness with the magnetic layer is significantly improved. As the main component of this coating layer, for example, a polyester resin or an acrylic resin can be cited.

As the acrylic resin, known resins can be adopted and are not particularly limited, but those containing an alkyl acrylate or an alkyl methacrylate as a main component are preferable, and 30 to 90 mol% of the component can be copolymerized with these. In addition, the vinyl monomer component having a functional group is 70 to
A water-soluble or water-dispersible resin containing 10 mol% is preferable.

As the polyester resin, a known polyester resin can be used and is not particularly limited, but in the copolyester ether resin, 60 mol% or more of the total dicarboxylic acid component is an aromatic dicarboxylic acid, and 7 to 40% mol% is an ester. It is preferable that the alkali sulfonic acid alkali metal salt compound is 40% by weight or more of all glycol components, and aliphatic or alicyclic glycol is 0 to 60% by weight of diethylene glycol or triethylene glycol.

If necessary, each of the above resins may contain a defoaming agent, a coatability improving agent, a thickening agent, an antistatic agent, an antioxidant, an ultraviolet absorber, a dye, a pigment and the like. Also,
The thickness of the coating layer is not particularly limited, but 1 to 1000
nm, especially 10-200 nm is preferred.

In the film of the present invention, different polymers may be blended within the range not impairing the object of the present invention, and antioxidants, heat stabilizers, lubricants, ultraviolet absorbers, etc. may be blended. The organic additives may be added to the extent that they are usually added.

Next, the method for producing the film of the present invention will be described in the case of a polyester film. First, as a method for incorporating particles in polyester, for example, a method is preferred in which particles are dispersed in a predetermined ratio in ethylene glycol, which is a diol component, and the ethylene glycol is polymerized with a predetermined dicarboxylic acid component. When adding particles, for example, if the water sol or alcohol sol obtained at the time of synthesis is added without being dried once, the dispersibility of the particles is very good, and the winding property and the dropout property are both good. You can Further, a method in which an aqueous slurry of particles is directly mixed with a predetermined polyester pellet and supplied to a vent type twin-screw kneading extruder and kneaded into polyester is also very effective in further improving the effect of the present invention. As a method of adjusting the content and number of particles, a high-concentration particle master is prepared by the above method, and the particle content is adjusted by diluting it with a polyester that does not substantially contain particles during film formation. The method is effective.

Next, the polyester pellets are used to form a polyester film having a laminated structure of three or more layers. The polyester pellets obtained by the above method are mixed at a predetermined ratio, dried, and then supplied to a known melt laminating extruder, extruded into a sheet from a slit-shaped die, and cooled and solidified on a casting roll. At the very least make an unstretched film. That is, using two or three or more extruders, three or more layers of manifolds or merging blocks (for example, merging blocks having a square merging portion), the film layers forming the outermost layers and the film layers forming the intermediate layers are used. Are laminated and coextruded from the die as a sheet of three or more layers,
Cool on a casting roll to make an unstretched film. In this case, the method of installing a static mixer and a gear pump in the polymer channel is effective. Further, it is effective to lower the melting temperature of the extruder for extruding the polymer on the outermost layer laminated portion side by 5 to 10 ° C. lower than that on the base layer portion side.

Next, this unstretched film is biaxially stretched to be biaxially oriented. As a stretching method, a sequential biaxial stretching method or a simultaneous biaxial stretching method can be used. However, a sequential biaxial stretching method of first stretching in the longitudinal direction and then in the width direction is used, and stretching in the longitudinal direction is performed in three or more stages, and the total longitudinal stretching ratio is 3.5 to 6.5 times. The method is particularly preferred. The stretching temperature in the longitudinal direction varies depending on the type of polyester and cannot be generally stated, but the first stage is usually 50 to 1
It is effective to set the temperature to 30 ° C. and raise the temperature from the second stage onward. The longitudinal stretching speed is 5000 to 50000% /
The range of minutes is preferred. As a stretching method in the width direction, a method using a stenter is generally used. The draw ratio is 3.0
The range of up to 5.0 times is suitable. The stretching speed in the width direction is
The range of 1000 to 20000% / min and the temperature of 80 to 160 ° C are suitable. Next, this stretched film is heat-treated. The heat treatment temperature in this case is 170 to 220 ° C., especially 1
The range of 80 to 200 ° C. and the time of 0.2 to 20 seconds are suitable.

The coating layer containing a water-soluble or water-dispersible resin as a main component is preferably provided by coating. The coating may be performed after uniaxial stretching or after biaxial stretching. It is also possible to wind the biaxially stretched film once and then rewind it off-line for coating. It is also possible to coat at the stage of the unstretched film, but in the case of the sequential biaxial stretching method, since the film comes into contact with a plurality of rolls in the longitudinal stretching, it is not preferable to coat at the stage of the unstretched film. . In the case of the simultaneous biaxial stretching method,
It is also possible to coat at the stage of unstretched film.

[Physical property measuring method and effect evaluating method] The characteristic value measuring method and effect evaluating method of the present invention are as follows. (1) Average particle size and number of particles The polymer is removed from the film by a plasma low temperature ashing method to expose the particles. The processing conditions are such that the polymer is incinerated but the particles are not damaged as much as possible. The particles are observed with a scanning electron microscope (SEM), and the particle image is processed with an image analyzer. The magnification of SEM is approximately 2000 to 10000 times, and the visual field in one measurement is appropriately selected from approximately 10 to 50 μm on each side. The volume average diameter d is obtained from the particle diameter and its volume fraction with the number of particles of 5000 or more by changing the observation location. d = Σd _i · Nv _i where d _i is the particle size and Nv _i is the volume fraction thereof. The number of particles is calculated from the volume fraction and converted per mm ² for those satisfying the relationship between the laminated thickness and the average particle diameter. When the particles are organic particles or the like and are significantly damaged by the plasma low temperature ashing method, the following method may be used. Using a transmission electron microscope (TEM), the film cross section is 30
Observe at 00-100,000 times. The section thickness of the TEM is set to about 1000Å, the location is changed and 500 or more visual fields are measured, and the volume average diameter d is obtained from the above formula.

(2) Thickness of laminated polyester layer (thickness of outermost layer: t) Using a secondary ion mass spectrometer (SIMS), the highest thickness among the particles in the film in the depth range from the surface layer to 3000 nm The concentration ratio (M ⁺ / C ⁺ ) of the element due to the concentration of particles and the carbon element of polyester is defined as the particle concentration, and the analysis is performed in the thickness direction from the surface to a depth of 3000 nm. In the surface layer, the particle concentration is low due to the interface of the surface, and the particle concentration increases as the distance from the surface increases. In the case of the film of the present invention, the particle concentration once reaching the maximum value starts to decrease again. Based on this concentration distribution curve, the depth at which the surface layer particle concentration becomes ½ of the maximum value (this depth is deeper than the maximum value) was determined and used as the laminated thickness. The conditions are as follows. Measuring instrument Secondary ion mass spectrometer (SIMS) A-DIDA3000 manufactured by ATOMIKA, West Germany Measuring conditions Primary ion species: O ₂ ⁺ Primary ion accelerating voltage: 12KV Primary ion current: 200nA Raster area: 400μm □ Analysis area: Gate 30% Measured vacuum degree: 6.0 × 10 ^-9 Torr E-GUN: 0.5KV-3.0A If the most contained particles in the depth range from the surface layer to 3000 nm are organic polymer particles, SIMS Since it is difficult to measure with XPS (XPS (X
The layer thickness may be obtained by measuring a depth profile similar to the above by line photoelectron spectroscopy), IR (infrared spectroscopy), or the like, or by observing a cross section with an electron microscope or the like, the state of change in particle concentration or polymer It is also possible to recognize the interface from the difference in contrast due to the difference and obtain the laminated thickness. Furthermore, after peeling the laminated polymer, the laminated thickness can be obtained using a thin film step measuring machine.

(3) Number of projections on the film surface The film surface was measured using a two-detector scanning electron microscope [ESM-3200, manufactured by Elionix Co., Ltd.] and a cross-section measuring device [PMS-1, manufactured by Elionix Co., Ltd.]. The height measurement value of the protrusion when scanning is performed with the height of the flat surface set to 0 is sent to an image processing apparatus [IBAS2000, manufactured by Carl Zeiss Co., Ltd.] to reconstruct the film surface protrusion image on the image processing apparatus. Next, the highest value among the individual projections obtained by binarizing the projections in this surface projection image is taken as the height of the projection, and this is calculated for each projection. This measurement was repeated 500 times at different places, and those having a height of 20 nm or more were used as protrusions to determine the number of protrusions. The magnification of the scanning electron microscope is selected to be 1000 to 8000 times. In some cases, a high-precision optical interference type three-dimensional surface analyzer (WY
KO TOPO-3D, objective lens: 40-200
The height information obtained by using a double high-resolution camera is effective) may be used instead of the SEM value.

(4) Dropout Evaluation on Magnetic Tape A VTR was used for the created magnetic tape, and after recording a signal from a TV test signal generator (TG-7 / 1 type manufactured by Shiba Soku), 25 ° C., 50% 100 passes by RH (120 minutes x 1
(00 pass). Using a dropout counter, a tape having a dropout width of 5 μsec or more and a reproduced signal attenuation of −16 dB or more was picked up as a dropout. The measurement is 1
Do 0 rolls, and if the number of dropouts converted per minute is less than 10, the dropout is good.
The case of 0 or more was regarded as defective.

(5) Adhesiveness with magnetic layer A commercially available polyester adhesive tape is attached to the magnetic film so as to have a length of 20 cm, and is peeled off at a stretch. The total light transmittance of the coating peeling portion was measured with a haze meter SEP-H-2 type manufactured by Nippon Seimitsu Optical Co., Ltd., and the remaining amount of the coating was determined by the following formula to determine the adhesiveness. Remaining amount of magnetic coating peeling D = (T ₀ −T ₁ ) / T ₀ × 100 (%) where T ₀ : total light transmittance (%) before application of magnetic coating (raw) T ₁ : magnetic Total light transmittance (%) of the peeled-off portion of the coating film was evaluated as having a D value of less than 70% as an adhesive property: poor, and having a D value of 70% or more as an adhesive property: good.

(6) Winding characteristics The film was wound up on a roll having a width of 1000 mm and a length of 15000 m (speed: 300 m / min), the end face displacement of this winding roll and the state of vertical wrinkles were inspected in detail and judged as follows. . End face deviation (distance in the width direction) is 0.5
Less than 0.5 mm, no vertical wrinkles and no defects such as vertical wrinkles even after standing for 24 hours or more: excellent, end face shift was less than 0.5 mm immediately after winding the roll, and no vertical wrinkles 24 Visually slight vertical wrinkles after standing for at least the time: good, misalignment of 0.5 mm or more, or slight vertical wrinkles immediately after winding the roll: bad. Good is desirable, but good is practically usable.

[0030]

EXAMPLES Next, the embodiments of the present invention will be explained based on examples. Example 1 (Table 1) The particles to be contained in the outermost layer were added in ethylene glycol.
Disperse glass beads with a diameter of 50 μm as media,
After removing the glass beads, it was polymerized with terephthalic acid to obtain polyethylene terephthalate master pellets.

The above master pellets were diluted with polyethylene terephthalate pellets containing no particles at a predetermined ratio and dried under reduced pressure (3 Torr) at 180 ° C. for 8 hours, and then the extruder 1 and the extruder 2 (for example, a vented twin screw). It was supplied to a kneading extruder) and melted at 280 ° C and 290 ° C. Each of these two polymers was filtered with high precision, then formed into a sheet of three layers by a three-layer merging block equipped with a rectangular laminated portion and discharged from a fish-tail type mouthpiece, and the electrostatic applied casting method was used. Wrap it around a casting drum with a surface temperature of 25 ° C to cool and solidify to a thickness of about 16
An unstretched film of 0 μm was made. The draft ratio at this time was 6.5.

This unstretched film was stretched 3.3 times in the longitudinal direction by roll stretching at 90 ° C. Next, one surface of this uniaxially stretched film was subjected to corona discharge treatment in an air atmosphere, and the treated surface had a concentration of water-dispersible acrylic resin'Nikazol 'A-08 [manufactured by Nippon Carbide Industry Co., Ltd.] of 1.0. After coating the coating material with a weight% by using a metalling bar coater, while drying the coating layer, the film is stretched in the transverse direction by 3.6 times at 105 ° C. and heat-treated at 210 ° C. for 5 seconds to form a coating layer thickness. A 14 μm-thick laminated film coated with a 25 nm coating layer was obtained. The thickness t of the outermost layer of the obtained film was 800 nm, and the relationship t / d between the thickness t of the outermost layer and the average particle diameter d of the contained particles was 1.3. Also,
The number of protrusions on both surfaces is the same, and the number of protrusions on the surface is 2200.
The number was 0 / mm ² . Furthermore, t / d is 0.2 to 10
The number of particles was 19000 / mm ² .

The winding property of this film was excellent, and the adhesiveness to the magnetic layer was also good. When the dropout of the VTR tape made from this film was evaluated, it was good. Thus, in the case where the relationship between the particles contained in the outermost layer laminated portion and the laminated thickness, the number of particles satisfying the relation, the number of surface protrusions is within the scope of the present invention, and a specific coating layer is provided, Excellent winding characteristics, adhesion to the magnetic layer, and dropout characteristics can be obtained.

Examples 2 to 4 and Comparative Examples 1 to 5 (Table 1) In the same manner as in Example 1, the lamination thickness of the outermost layer, and the relation t between the lamination thickness t and the average particle diameter d of the contained particles, t. / D, the number of surface protrusions, the number of particles having a t / d of 0.2 to 10, and the type of the coating layer were changed variously, and various biaxially oriented laminated polyester films were prepared in the case where the coating layer was not provided ( However, Comparative Example 5 is a single layer film). Thickness of the outermost layer, relationship between the thickness t and the average particle diameter d of the contained particles t /
When d, the number of surface protrusions, and the number of particles having a t / d of 0.2 to 10 are within the scope of the present invention and a specific coating layer is provided, excellent winding characteristics and excellent magnetic properties are obtained. Adhesiveness and dropout characteristics were obtained (Examples 2 to 4), but when the requirements specified in the present invention were not satisfied, even if some conditions were within the scope of the present invention, winding characteristics It was not possible to satisfy all of the adhesiveness with the magnetic layer and the dropout characteristics (Comparative Examples 1 to 4).

[0035]

[Table 1]

[0036]

According to the biaxially oriented laminated film of the present invention, the outermost layer on at least one side of a laminated structure of at least three layers satisfies a specific particle average particle diameter and the layer thickness of the outermost layer. As described above, since the number of surface protrusions or the number of particles having a particle size satisfying the above relation is set within a specific range and a specific coating layer is provided on the surface of the laminated film, it is difficult for the surface of the laminated film to be scraped. In addition, desired protrusions can be efficiently formed to have a desired surface morphology, and excellent winding characteristics and excellent dropout characteristics for magnetic media can be obtained, as well as excellent adhesion to a magnetic layer. be able to.

Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display area B29L 9:00 4F

Claims (3)

[Claims] 1. A biaxially oriented laminated film having a laminated structure of at least three layers formed by coextrusion, wherein particles are contained in at least one outermost layer of the film, and the average particle diameter d (nm) of the particles and The relation with the layer thickness t (nm) of the outer layer is 0.2d ≦ t ≦ 10d, and the number of protrusions on the film surface on the outermost layer side is 3 × 1.
0 ³ a to 2 × 10 ⁵ cells / mm ^2, further that at least on one side, a biaxially oriented laminated film which is characterized in that a coating layer mainly composed of water-soluble or water-dispersible resin. 2. A biaxially oriented laminated film having a laminated structure of at least three layers formed by coextrusion, wherein particles are contained in at least the outermost layer on one side, and the average particle diameter d (nm) of the particles and The relationship with the layer thickness t (nm) of the outer layer is 0.2d ≦ t ≦ 10d, and the number of particles having a particle size satisfying the relationship is 3 × 10 ^3.
To 1.5 × 10 it was ⁵ pieces / mm ^2, further that at least on one side, a biaxially oriented laminated film which is characterized in that a coating layer mainly composed of water-soluble or water-dispersible resin. 3. The biaxially oriented laminated film according to claim 1, wherein the main component of the coating layer is a polyester resin or an acrylic resin.